The quality or state of being abnormal; deviation from what is normal or typical.
From abnormal + -cy (abstract noun suffix). Modern formation combining the adjective 'abnormal' (from Latin ab- + norma, rule) with a suffix indicating a state or condition.
Most people say 'abnormality' but 'abnormalcy' exists and is rarer—it's the kind of word that slipped into dictionaries because English speakers sometimes preferred the '-cy' suffix, even though it didn't catch on widely!
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